1. Field of the Invention
This invention relates to an article having two sections which are articulated together through a hinge, and to a mold for use in manufacturing the article. More specifically, this invention relates to a rigid article having two sections which are articulated together through a ball and socket-type hinge which is simultaneously molded with the sections of the article in an assembled and operative condition, and to a mold for use in manufacturing the article.
2. Description of the Prior Art
Rigid plastic containers including a two-piece hinge connecting a lid to a container body have many commercial applications. One specific application is in the bulk packaging of relatively small articles, such as nails, bolts, screws, nuts and the like. These containers have been displayed or stored in bins, or alternatively, have been provided with annular openings to permit them to be displayed or stored on supporting rods connected to a peg board or a similar supporting structure.
Until the advent of the invention disclosed in U.S. Pat. No. 3,456,913, issued on July 22, 1969 to the inventor of the subject matter of this invention, it was common practice to mold one portion of a two-piece hinge with the body of the container and the other portion of the hinge with the lid of the container. However, the two pieces of the hinge were not molded in an engaged and operative condition. Accordingly, a separate and independent step of mating the lid and container body through their hinge pieces was required. This approach adds expense and time to forming the containers, as compared to a process in which the containers are initially molded with the hinge pieces in an assembled and operative condition. Moreover, when the containers are formed of substantially ridgid plastic material, or have delicate hinge parts of very thin dimensions, the assembly operation is difficult, and can cause damage to the hinge.
U.S. Pat. No. 3,456,913, disclose a mold for use in integrally molding hinged plastic containers with the hinge pieces engaged in their operative condition. Specifically, the container disclosed in the U.S. Pat. No. 3,456,913 includes a pintle 18 of a male hinge member extending through an eye 17 of a female hinge member. The pintle 18 is generally of very thin proportions, and therefore may break if an undesirable torque is imposed upon it. Moreover, the outside diameter of the pintle is less than the inside diameter of the eye, and this structural relationship inherently follows from the mold configuration employed to form the hinge. Accordingly, the hinge includes some play in it. For some applications this loose fitting relationship between male and female hinge members may not be desired.
The mold disclosed in the U.S. Pat. No. 3,456,913 is somewhat complex, and includes thin wall sections which may become damaged by fragments of molded material which are inadvertently left in the mold after an injection molding operation. These fragments may cause the thin wall sections to break when the mold sections are closed for a subsequent molding operation.
The complexity of the mold disclosed in the U.S. Pat. No. 3,456,913 results from the fact that it includes core pins 34 which must be moved laterally into sliding engagement with a seat 38 provided by surfaces of upper and lower mold sections which are moved vertically with respect to each other. Accordingly, the mold requires a cam mechanism for affecting the lateral movement of the core pins as the upper and lower mold sections are moved vertically into a closed, injection molding condition. Moreover, the mold requires some retracting mechanism for withdrawing the core pins from the mold after the injection molding operation has been completed. The inclusion of the above-described camming and retracting mechanisms in a mold enhances its complexity.
The core pins 34 employed in the mold disclosed in the U.S. Pat. No. 3,456,913 include a hollow head portion 36 which, in the closed condition of the mold, tightly engages surfaces of the upper and lower mold sections which define seat 38. When the mold is in its closed condition the hollow portion of each head 36 communicates with a male hinge member forming cavity 27. The peripheral wall defining the hollow head portion 36 is quite thin. Therefore, any plastic fragments which are inadvertently left on the surfaces defining seat 38, or within the male hinge member forming cavity 27, may cause the head portion 36 to break, or otherwise become damaged, as the mold is closed to perform a subsequent injection operation. Furthermore, sliding frictional engagement between the core pins 34 and the mold seats for the pins can cause undesirable wear of the frictionally engaged surfaces.
U.S. Pat. Nos. 2,687,157 (Cowan); 2,778,533 (Savary); 2,875,472 (Marcus) and 3,013,308 (Armour) disclose single-piece, web-type hinges which are integrally injection molded with sections of an article that are to be articulated with respect to each other. The hinge arrangement disclosed in these patents, as well as the molds employed to form them, are somewhat nonanalogous to the instant invention which relates to the molding of two-piece hinges with the hinge pieces in an operative and engaged condition with respect to each other.